Industrial, commercial and municipal facilities located in regions that are subject to seasonal freezing and are required to draw quantities of water from rivers during the freezing season are subject to the negative effects of the buildup of frazil ice on gratings protecting water intakes from the ingestion of foreign objects and aquatic life. These negative effects can include, depending on the nature of the plant in question, lower operating efficiencies, loss of cooling water, damage to pump components, and loss of revenues due to unexpected down time.
Currently, the only detection and alarm systems in implementation consists of complex, mechanical systems with moving components that have low reliability and require significant maintenance.
Such a mechanical system is shown, for example, in U.S. Pat. No. 5,062,120. In contrast, it is an objective of the present invention to provide a simple, economical, reliable and low maintenance system for detecting and indicating the occurrence of the accretion of frazil ice on water intake gratings.
Frazil ice is formed when turbulent water is cooled. Once the water is supercooled a few hundredths of a degree, minute ice crystals form in the water and conglomerate, resulting in flocks of frazil ice. Frazil forms mainly in rivers but has been seen in lakes, cooling ponds and in the ocean where the surface is turbulent and there is ambient cooling. Many water intakes for power generation plants and other industrial and commercial processing plants have waterway approaches that have turbulent flow, a prime condition for the formation of frazil ice. As long as the water temperature is at or below freezing, it is possible for frazil ice to form. Once formed, frazil ice will adhere to, and continue to accrete on, practically any natural or man-made object in the water, including: rocks, wood, and metal structures (including protective gratings over water intakes known in the industry as "trash racks"). Under certain frazil growth conditions, trash racks on water intakes have been known, without warning, to completely occlude in a matter of a few hours.